NUMERICAL-STUDIES ON LAMINARIZATION OF HEATED TURBULENT GAS-FLOW IN ANNULAR DUCT

Heated turbulent gas flow in an annular duct is numerically analyzed using the k-kL-uvBAR 3-equation turbulence model. Special attention is paid to the laminar-turbulent transitional region. In the case of outer tube only heated, heat transfer coefficient in downstream becomes constant and a new correlation, which is independent of the heat flux, is proposed. The similar result is obtained in the case of inner tube only heated. In the case of both inner and outer tubes heated, laminarization does not occur under the condition of the heat flux less than a certain magnitude on one tube and it does not depend on the heat flux magnitude on the other tube. The flow regime of heated annular duct is classified into the following four regions based on heated conditions of inner and outer tubes: (1) TT region (heat transfer coefficients in both tubes are expressed by St(b) is-proportional-to Re(b)-0.2), (2) LT region (heat transfer coefficient in inner tube becomes constant), (3) TL region (heat transfer coefficient in outer tube becomes constant) and (4) LL region (laminarization occurs).